It is well known to use a flash light source such as a xenon tube to illuminate objects when taking pictures.
In a conventional flash device, spectral characteristics defined for one flash device cannot be varied by the operator. Accordingly, when such a conventional flash device is used as an auxiliary illuminating light source for an object to be photographed under such conditions that the main light source is fed from fluorescent tubes or the picture is taken in the evening glow, there sometimes occurs a difference of spectral characteristics between the main light source and the auxiliary light source, thereby resulting in nonuniform color shading in a printed picture due to the difference of distribution of light.
In a case where a flash light is used for a main light source, i.e., the object is illuminated only by the flash light, if the spectral characteristic of a given film is not suitable for that of the flash light, e.g., in the case when a film of tungsten type is used with the flash light emitted by a xenon tube, an unnatural color print may be obtained.
Furthermore, when taking a picture, a color correction filter is often used for compensating the spectral difference between the main illuminating light source and a light sensing member such as a film, there may occur color shading in a printed picture if a flash device is used as an auxiliary light source, the spectral characteristic of which is different from that of the main light source. In general, when an object to be photographed is illuminated by two kinds of light sources, color compensation by color correction filters cannot be expected.
As understood from the foregoing, the conventional flash devices show a disadvantage in that they cannot provide a good light for illuminating the object in various cases as mentioned above to obtain a good print having uniform color distribution.
A color enlarger for photographic color printing is known in which a plurality of lamps such as halogen lamps having flat spectral distribution characteristics of the emitted light are used with various filters each having different spectral characteristics placed in front of the respective halogen tubes so that desired spectral characteristics, e.g., color temperature can be obtained by controlling the amount of the compensation with the filters.
However the above mentioned device is very complicated and cumbersome in construction and so expensive that the device is not suitable for use in an electronic flash device. Furthermore, since the device must be supplied with power from a commercial power source, it is not suitable for use as a main light source or an auxiliary light source for illuminating an object to be photographed.